Power takeoff control system

ABSTRACT

A control system is disclosed for controlling a power takeoff (PTO) shaft of a work vehicle (e.g., a tractor). The work vehicle includes an engine and an operator station, and the PTO shaft transfers power from the engine to an implement. The control system includes a remote switch, a vehicle speed sensor, and a control circuit. The remote switch is located remotely from the operator station and provides a remote switch signal to the control circuit to engage and disengage rotational movement of the PTO shaft. The vehicle speed sensor provides a vehicle speed signal to the control circuit representative of a speed of the work vehicle. The control circuit receives the remote switch signal and the vehicle speed signal and, when the vehicle speed signal exceeds a predetermined vehicle speed, the control circuit prevents engagement and disengagement of the PTO shaft with the remote switch.

FIELD OF THE INVENTION

The present invention relates generally to control systems forengagement and disengagement of a power takeoff. More specifically, thepresent invention relates to control systems for engagement anddisengagement of a power takeoff shaft of a work vehicle such as atractor.

BACKGROUND OF THE INVENTION

Many work vehicles (e.g., agricultural vehicles such as tractors;construction vehicles such as skid-steers) in use today include at leastone power takeoff (PTO) shaft. A PTO shaft allows the farmer to operateimplements and other farm machinery using power provided by the tractorengine. Common PTO-driven implements include balers, mowers, grindermixers, augers, drills, etc. Some of these implements are driven whilethe tractor travels across a field (e.g., balers and mowers) whileothers are driven while the tractor is stationary (e.g., augers, drills,blowers, feeders, grinders and manure pumps). Still others may be drivenwhile the tractor is either stationary or traveling (e.g., grindermixers).

Ease of operator use and flexibility of controls are importantconsiderations when designing an operator control system for PTOs. Insome prior systems, a control switch has been provided in the operatorstation (e.g., cab or platform) of the work vehicle to allow theoperator to engage and disengage the PTO shaft to the engine of the workvehicle. These operator station-mounted switches are useful forapplications where the tractor is in motion since the operator istypically in the operator station while farming. However, when an augeror drill is driven by the PTO shaft, the operator must continuously walkback to the operator station to turn the PTO shaft on and off using theoperator station-mounted switch.

Accordingly, remote switches have been mounted at various locationsaround the work vehicle (e.g., on the front or rear fender of thevehicle) to allow the operator to control the PTO from outside theoperator station of the work vehicle. Various control systems have beenintroduced to determine when the remote switch is active and when theoperator station-mounted switch is active. For example, in one priorsystem, a selector switch is provided in the operator station to selectbetween a standard mode (operator station-mounted switch active) and aremote mode (fender-mounted switch active). One drawback of this controlsystem occurs when the operator wishes to switch from remote mode backto standard mode. The operator must actively switch the system from theremote mode to the standard mode when the operator enters the vehicleand begins farming the field with a PTO-driven implement. If theoperator forgets to actuate this selector switch, the remote switch isstill active. Thus, a stray twig, stalk or other obstruction may actuatethe remote switch, turning the remote PTO on or off unbeknownst to theoperator, causing operator confusion. The operator may also travel somedistance before realizing this error, requiring the operator to re-farmthe missed portion of the field, wasting valuable time and resources.

Farm equipment manufacturers are beginning to realize the advantages ofautomating certain controls on the work vehicle. For example, when thework vehicle reaches the end of a row in the field (i.e., the headland),the operator must perform several tasks at once, including such thingsas turning the PTO shaft off, raising the hitch which is coupled to theimplement, disabling mechanical front-wheel drive (MFD), disablingdifferential lock (DL), etc. Then, as the tractor re-enters the fieldafter turning around on the headland, the operator must perform theopposite of these same tasks. Thus, attempts have been made in the priorart to automate one or more of these tasks performed when the workvehicle reaches the headland. Additional functionality and flexibilityis demanded by operators to allow them to customize this automationprocedure for various farming processes.

Accordingly, what is needed is an improved control system for a PTOhaving remote switches which improves the ease of use of the remoteswitches without significantly affecting operability or functionality.Also what is needed is a system to add new functionality and flexibilityto the automation of PTO control when the work vehicle reaches and turnsaround on the headland.

SUMMARY OF THE INVENTION

These and other limitations of the prior art are overcome by the presentinvention which, according to an exemplary embodiment, includes acontrol system for controlling a power takeoff shaft of a work vehiclehaving an operator station. The control system includes a remote switch,a vehicle speed sensor and a control circuit. The remote switch islocated remotely from the operator station and provides a remote switchsignal to control the power takeoff shaft. The vehicle speed sensorprovides a vehicle speed signal representative of a speed of the workvehicle. The control circuit, coupled to the remote switch and thevehicle speed sensor, receives the remote switch signal and the vehiclespeed signal. When the speed of the work vehicle exceeds a predeterminedspeed, the control circuit prevents control of the power takeoff shaftwith the remote switch signal.

According to another exemplary embodiment of the present invention, acontrol system for controlling a power takeoff shaft of a work vehiclehaving an operator station is provided. The control system includesremote switch means for providing a remote switch signal to control thepower takeoff shaft, and a vehicle speed sensor means for providing avehicle speed signal representative of a speed of the work-vehicle. Thecontrol system further includes control means coupled to the remoteswitch means and the vehicle speed sensor means for receiving the remoteswitch signal and the vehicle speed signal and, when the speed of thework vehicle exceeds a predetermined vehicle speed, for preventingcontrol of the power takeoff shaft with the remote switch signal.

According to another exemplary embodiment of the present invention, amethod for controlling a power takeoff shaft of a work vehicle isprovided. The method includes providing a remote switch signal tocontrol the power takeoff shaft, providing a vehicle speed signalrepresentative of a speed of the work vehicle, and preventing control ofthe power takeoff shaft with the remote switch signal when the speed ofthe work vehicle exceeds a predetermined vehicle speed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingdrawings, wherein like reference numerals refer to like parts, and inwhich:

FIGS. 1A-1B are diagrams of a tractor having a PTO shaft capable ofdriving implements while traveling (FIG. 1A) and while stationary (FIG.1B) according to an exemplary embodiment of the present invention;

FIG. 2 is a block diagram of the control system for the tractor andimplement of FIGS. 1A and 1B according to an exemplary embodiment of thepresent invention;

FIG. 3 is a flow chart showing the control flow of the control system ofFIG. 2 according to one feature of the present invention; and

FIG. 4 is a diagram of an alternative embodiment of the exemplaryoperator interface unit shown in FIG. 1A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1A, a work vehicle 10 is shown pulling an implement12. Work vehicle 10 may be any type of agricultural or constructionvehicle, such as, a Case Model 4240 tractor. Implement 12 may be anytype of implement, such as, a rotary harrow, for example, a Lelyterra35/45-series rotary harrow. Vehicle 10 includes an operator station 14,a hitch 16 and a power takeoff (PTO) shaft 18. Vehicle 10 furtherincludes a control unit 64 coupled to a pair of remote PTO controlswitches 22, 24, a remote hitch control switch 23, a vehicle speedsensor 25, a hitch position sensor 27 and an operator interface unit 20.The positioning of switches 22, 23 and 24 is selected to allow a directview of a drive shaft 26 of implement 12 by an operator standing behindvehicle 10 using switches 22, 23 and 24. In one embodiment, remote PTOswitches 22 and 24 are located outboard of rear brake lights 31, 33 onleft and right fenders 35. Remote hitch control switch 23 is locatedinboard of rear brake light 31. A second remote hitch control switch canbe similarly located inboard of brake light 33. Operator interface unit20 includes PTO control switches 2 and hitch control switches 4. PTOcontrol switches 2 include an operator station-mounted PTO ON/OFFcontrol switch 1, a PTO remote/local selector switch 3 and an auto PTOmode switch 5. Hitch control switches 4 include a hitch position commandswitch 9 and a hitch UP/DOWN switch 11.

Implement 12 is coupled to vehicle 10 at hitch 16 and further includes adrive shaft 26 and a driven member 28. Hitch 16 may be, for example, athree-position hitch such as that shown in commonly assigned U.S. Pat.No. 5,421,416 to Orbach et al. entitled “Hitch Assembly Control System”or commonly assigned U.S. Pat. No. 5.601,146 to Schlegel et al. entitled“Hitch Assembly for a Tractor,” both patents hereby incorporated byreference. In this embodiment, driven member 28 is a blade for a mower.PTO shaft 18 is engaged to the engine (not shown) of vehicle 10 inresponse to control signals from control circuit 64. In response, PTOshaft 18 begins rotating at, for example, 540 or 1000 rotations perminute, driving at 40 to 150 horsepower or more. Since PTO shaft 18 iscoupled to drive shaft 26 which is itself coupled to driven member 28,as vehicle 10 traverses an agricultural field, the engine of vehicle 10provides the necessary power to drive the driven member 28 to therebywork a field. According to one advantageous feature of the presentinvention, while vehicle 10 is travelling, remote PTO control switches22, 24 are disabled to prevent inadvertent actuations as describedhereinafter.

Referring now to FIG. 1B, vehicle 10 is shown coupled to a secondimplement 30. Second implement 30 is, for example, a Case Model 1260grinder-mixer. Implement 30, like implement 12, includes a drive shaft32 and one or more driven members 34, 36 (e.g., a hammermill, an augerfeeder, etc). Again, since PTO shaft 18 is coupled to drive shaft 32which is itself selectively coupled to one or more of driven members 34,36, the engine of vehicle 10 provides the necessary power to drivedriven members 34, 36 for loading, grinding, mixing, and unloading feedor other product. In this embodiment, vehicle 10 is stationary whiledriven members 34, 36 of implement 30 are driven. Accordingly, anoperator 38 standing outside vehicle 10 uses remote PTO switches 22, 24(see FIG. 1A) for convenience to engage and disengage PTO shaft 18.

Referring to FIG. 2, a PTO control system 50 for vehicle 10 is shown.One example of a PTO control system is disclosed in commonly assignedapplication Ser. No. 09/262,713, filed Mar. 4, 1999, entitled “PowerTake Off Engagement Control System”, which is hereby incorporated byreference. An engine 52 provides power to the drive wheels (not shown)of vehicle 10 and, in addition, provides power to apply rotationalmotion to a multi-plate, hydraulically-actuated PTO clutch 54. An outputshaft 56 of clutch 54 is shown directly coupled to a 1000 RPM PTO (highspeed PTO) shaft 18 and optionally coupled to a 540 RPM PTO (low speedPTO) shaft 60 by a reduction gear 62. In the embodiment shown, PTO shaft18 is used to drive the implement. In alternative embodiments, PTO shaft60 could drive the implement, or other PTO speeds may be used.

Control system 50 includes a control circuit 64 (e.g., including one ormore digital microprocessors such as an Intel TN83C51FA microprocessoror other digital or analog circuitry, a memory, inputs/outputs, etc.)coupled to operator station-mounted PTO ON/OFF control switch 1, PTOremote/local selector switch 3, auto PTO mode switch 5, hitch positioncommand switch 9, hitch UP/DOWN switch 11, remote PTO control switches22, 24, remote hitch control switch 23, vehicle speed sensor 25, hitchposition sensor 27 and a hydraulic clutch control valve 68. Vehiclespeed sensor 25 includes a ground speed radar, but may alternativelyinclude a transmission output speed sensor which counts the teeth in aring gear of the transmission of vehicle 10 to determine if the vehicleis moving. Vehicle speed sensor 25 may alternatively include a wheelspeed sensor or other system for providing a signal indicative of thespeed of vehicle 10. Hydraulic clutch control valve 68 is controlled bycontrol circuit 64 to selectively engage and disengage PTO clutch 54 viaa hydraulic conduit 69. When PTO clutch 54 is engaged, power from engine52 is transmitted to output shaft 56. Control system 50 may furtherinclude a hydraulically-actuated or spring-actuated brake 70 to inhibitrotational motion of output shaft 56 when PTO clutch 54 is disengaged.Control system 50 includes a hydraulic valve 72 connected to brake 70 bya hydraulic conduit 74 to engage and disengage brake 70. Control circuit64 provides control signals to valves 68, 72 (e.g., analog or digitalsignals, pulse-width modulated (PWM) signals, amplitude-modulated orfrequency-modulated signals, or other control signals.)

Also shown in FIG. 2 is an implement 12, 30 that may be coupled tovehicle 10. Implement 12, 30 includes driven members 75 (e.g., drivenmember 28, driven members 34, 36) which are operated using power fromengine 52 when clutch 54 is engaged. Implement 12, 30 receives powerfrom engine 52 via drive shaft 26, 32 coupled, in this embodiment, tohigh speed PTO shaft 18 via a coupler 76. When PTO clutch 54 is engagedand is transmitting power from engine 52 to output shaft 56 and highspeed PTO shaft 18, power is transmitted to implement drive shaft 26, 32and to driven members 75 to perform one or more of a plurality ofimplement functions.

Remote PTO

According to one feature of the present invention, control circuit 64receives remote control signals from remote PTO control switches 22, 24,a local PTO control signal from operator station-mounted PTO controlswitch 1, and a vehicle speed signal from vehicle speed sensor 25. Inthe exemplary embodiment, remote PTO switches 22, 24 each include a pairof momentary pushbuttons and are mounted on opposite sides of vehicle 10and, preferably, on opposite sides of PTO shaft 18 (or low speed PTOshaft 60). Thus, the operator does not have to climb or reach overimplement drive shaft 26, 32 when the implement is coupled to PTO shaft18 to reach the remote control pushbuttons. Advantageously, remote PTOcontrol switches 22, 24 are located such that operator 38 standing onthe ground outside of operator station 14 has a direct view of implementdrive shaft 26, 32 from either remote switch location. When vehiclespeed sensor 25 indicates that vehicle 10 is travelling at or above apredetermined vehicle speed, e.g., one mile per hour (MPH), controlcircuit 64 prevents engagement or disengagement of PTO clutch 54 basedon the remote switch signal, effectively disabling remote PTO controlswitches 22, 24. This feature prevents inadvertent enabling anddisabling of PTO clutch 54 via remote PTO control switches 22, 24 whenvehicle 10 is in motion, such as, via a twig, stalk, or worker runningalongside vehicle 10. Preferably, operator station-mounted PTO controlswitch 1 is still enabled when vehicle 10 is travelling to allow theoperator within operator station 14 to engage and disengage the PTOshaft from operator station 14.

A flow diagram of a control flow according to an exemplary embodiment ofthis feature is disclosed in FIG. 3. The routine starts at step 100. Atstep 102, control circuit 64 determines if a signal is being receivedfrom operator station-mounted PTO control switch 1. If so, at step 104,control circuit 64 controls engagement or disengagement of the PTO basedon the signal received from operator station-mounted switch 1.Subsequently, the routine ends at step 106. If not, the control flowproceeds to step 108, to obtain a vehicle speed signal from vehiclespeed sensor 25 and scale it to engineering units (e.g., miles per hour,kilometers per hour, etc.). After step 108, the flow proceeds to step110 to test if the vehicle speed is greater than the predeterminedvehicle speed. As discussed hereinbefore, this predetermined vehiclespeed may be one MPH, less than one MPH, or more than one MPH (e.g., 10MPH) and may be programmable by a service technician or preset duringmanufacturing. If the measured speed is greater than the predeterminedvehicle speed, the control flow ends at step 106 without checking theremote PTO switches 22, 24, effectively disabling or disallowing controlof the PTO based upon the remote switch signal. Alternatively, theremote switch or switches are checked at step 112. If a remote switch ispressed, the PTO shaft is engaged or disengaged based on the remoteswitch position or signal at step 114. The routine may begin again atstep 100 and runs intermittently, selectively, or periodicallythroughout operation of the PTO.

Referring now to FIG. 4, an exemplary embodiment of operator interfaceunit 20 is shown with operator-adjustable switches in various exemplaryconfigurations. Various PTO control and hitch control switchconfigurations may be employed to facilitate operator control of the PTOshaft and hitch position. Switches 1, 3, 5, 9, 11, 22, 23 and 24 mayinclude any type of switch, such as, digital switches, analog switches,buttons, portions of a graphical user interface, etc., and may provideany type of control signal, such as, digital or analog signals. In thisexemplary embodiment, however, switches 1 and 3 are maintained,two-position switches. Switch 1 allows the operator, while at theoperator station, to manually engage or disengage the PTO shaft. Switch3 allows the operator to select between remote PTO switch control (i.e.,via remote PTO control switches 22, 24) and operator station-mounted PTOswitch control (i.e., via switch 1). Switch 5 is a three-position rockerswitch having an AUTO PTO OFF position (maintained), an AUTO PTO ONposition (maintained) and a SET position (momentary), the function ofwhich will be described hereinafter. Switch 9 is a slidable switch toallow the operator to set the position of the hitch relative to amaximum position and a minimum position. For example, when switch 9 isslid to a new position, control circuit 64 sends command signals toraise or lower the hitch at a predetermined speed until the selectedhitch position is attained. Switch 11 is a three-position momentaryswitch having an UP position (maintained), a first DOWN position(maintained) and a second DOWN position (momentary). Switch 11 commandscontrol circuit 64 to raise the hitch as long as the switch is in the UPposition or until the hitch reaches the maximum hitch height position,to lower the hitch as long as the switch is in first DOWN position oruntil the hitch reaches the minimum hitch height position, and to dropthe hitch, allowing gravity to pull the hitch to its lower-mostposition, when the operator actuates the second DOWN position twice inrapid succession.

In the embodiment of FIG. 4, the operator uses switch 3 to selectbetween remote PTO switch control and operator station-mounted PTOswitch control. Alternatively, switch 3 may be absent from controlinterface 20 and the operator may use either or both remote PTO controlswitches 22, 24 and operator station-mounted switch 1 at any time tocontrol engagement and disengagement of PTO shaft 18. In the formerembodiment, the operator cannot operate the PTO from the remote switcheswithout first entering the operator station to adjust switch 3 to itsREMOTE position, an inconvenience to the operator. In the latterembodiment, if operator station-mounted switch 1 is turned ON and one ofremote switches 22, 24 is used to turn the PTO OFF, operator confusionmay result when the operator returns to the operator station and wishesto turn the PTO ON when switch 1 is already in the ON position.

Accordingly, one advantageous modification includes the replacement ofswitch 1 and two-position switch 3 with a single three-position switchhaving a PTO OFF position (maintained), a PTO ON position (maintained)and an OFF CHANGE OF STATE position (momentary). In operation, with thevehicle being stationary, when the three-position switch is in the PTOOFF position, actuation of one of remote switches 22, 24 to the ONposition will override the PTO OFF signal from the three-position switchand the controller will engage the PTO. Actuating one of remote switches22, 24 to the OFF position will turn the PTO shaft off again. To turnoff the PTO shaft from inside the operator station after having turnedit on remotely, the operator moves the three-position switch to the OFFCHANGE OF STATE position momentarily, then releases it to disengage thePTO shaft. Thus, this feature allows the operator to turn off the PTOshaft from inside the operator station after it has been turned on withremote switches 22, 24 without operator confusion.

According to one embodiment, the three-position switch has a structurerequiring secondary motion in order to actuate the switch to the PTO ONposition For example, the three-position switch may have a button thatmust be pressed before the switch can be pulled upward into the PTO ONposition.

Remote PTO control switches 22, 24 each include, according to oneexemplary embodiment, a first ON pushbutton and a second OFF pushbutton.In order to turn the PTO on from remote switches 22, 24, control circuit64 requires the first ON pushbutton be pressed and held for apredetermined time (e.g., about 3 seconds) before the PTO shaft will beengaged. In order to turn the PTO off from remote switches 22, 24,control circuit 64 immediately turns the PTO off when the second OFFpushbutton is pressed. Furthermore, the surface of the second OFFpushbutton is raised a slight distance (e.g., 3-4 millimeters) higherthan the first ON pushbutton.

For PTO control from the operator station, the operator actuates thethree-position switch to the ON position which engages the PTO shaft. Asa further feature, the three-position switch can require two-motionactuation (i.e., lift and move) to prevent inadvertent engagement of thePTO shaft. The PTO shaft may then be disengaged by movement of thethree-position switch to OFF or OFF CHANGE OF STATE. With thethree-position switch in the ON position, the remote switches may stillbe used to engage and disengage the PTO shaft. Thus, this feature allowsthe operator to turn off the PTO shaft remotely after it has been turnedon from the operator station.

As a further feature, a PTO indicia 40 (e.g., a light emitting diode orother light or sound) is present on control interface 20. PTO indicia 40is steadily lit when the PTO is engaged from the operatorstation-mounted three-position switch and is turned off when the PTO isdisengaged from the three-position switch. When the PTO is turned on viathe three-position switch and subsequently turned off via remoteswitches 22, 24, PTO indicia 40 will flash, since the three-positionswitch is still in the ON position. To turn PTO indicia 40 off, thethree-position switch must be moved to its OFF position.

According to yet another feature, control circuit 64 will disable thePTO completely if a remote PTO OFF signal is received from remote PTOcontrol switches 22, 24 for more than a predetermined amount of time(e.g., 30 seconds), after which PTO indicia 40 will flash indicating aPTO control system error. However, if a remote PTO ON signal is receivedfrom remote PTO control switches 22, 24 for the predetermined amount oftime, control circuit 64 will wait until the operator turns the PTO offeither vian operator station-mounted switch 1 or via remote switches 22,24, after which control circuit 64 will disable PTO control using viaremote switches 22, 24.

Auto PTO

According to another advantageous feature of the present invention,engagement and disengagement of the PTO shaft is performed automaticallyby control circuit 64 when the work vehicle reaches the headland at theend of a row or re-enters the row after turning on the headland.Automatic control of the PTO shaft is based on the hitch position, asreceived from hitch position sensor 27, and the status of one or moreoperator-adjustable hitch position switches, such as, auto PTO modeswitch 5. According to one exemplary embodiment, control circuit 64includes a PTO controller to control engagement and disengagement of thePTO shaft and a hitch controller to control movement of the hitch and tosense the position of the hitch. The hitch controller provides data tothe PTO controller via a data bus (e.g., RS-485 or SAE J-1939 ControllerArea Network (CAN) bus), the data including the hitch position fromhitch position sensor 27, the setting of hitch position command switch9, the setting of hitch UP/DOWN switch 11, the setting of remote hitchcontrol switch 23 and a “hitch at upper limit” status signal when thehitch has reached its maximum position. The PTO controller also receivesdata from operator station-mounted PTO ON/OFF control switch 1, PTOremote/local selector switch 3 and auto PTO mode switch 5.

The operator begins AUTO PTO mode by first initializing a PTO OFF setpoint and a PTO ON set point. The PTO ON set point is a hitch positionbelow which the PTO will automatically engage when in AUTO PTO mode. ThePTO OFF set point is a hitch position above which the PTO willautomatically disengage when in AUTO PTO mode. To initialize set points,the operator moves the hitch to the desired set point and actuates autoPTO mode switch 5 to its SET position (momentary). One actuation setsthe PTO OFF set point and two actuations sets the PTO ON set point. Theset points may be initialized either with the PTO shaft rotating or withthe PTO shaft stationary, the former being preferred since it will allowthe operator to first identify “rattling” of the PTO shaft based on thehitch position and consequently set the set points to minimize thisrattling when the hitch is raised and lowered at the headlands.

Next, the operator selects AUTO PTO ON (maintained) using AUTO PTO modeswitch 5, PTO ON using operator station-mounted PTO ON/OFF controlswitch 1, and then begins traversing the field. As the operatorapproaches the headland, the operator raises the hitch using eitherhitch position command switch 9 or hitch UP/DOWN switch 11. The PTO isautomatically disengaged when the hitch is raised above the PTO OFF setpoint. As the operator drives out of the headland, the operator lowersthe hitch, again using either hitch position command switch 9 or hitchUP/DOWN switch 11. The PTO is automatically engaged when the hitch islowered below the PTO ON set point. An AUTO PTO indicia 42 (e.g., lightemitting diode, buzzer, etc.) is provided on operator interface 20 toindicate when AUTO PTO mode is active. Since the PTO shaft typicallytakes approximately 1.5 to 2.75 seconds to engage, including two setpoints instead of one allows the operator to set the PTO ON set point ata higher implement position than the PTO OFF set point to allow the PTOshaft to be rotating at full speed before the implement is completelylowered to the ground. Other advantages and features of this flexibletwo set point system will be apparent.

The system includes further features relating to the variouspermutations of inputs from auto PTO mode switch 5, operatorstation-mounted PTO switch 1, hitch position sensor 27, etc. Forexample, if operator station-mounted PTO switch 1 is moved to its OFFposition while auto PTO mode switch 5 is still in its AUTO PTO ONposition, the PTO will be disengaged regardless of hitch position sinceit is presumed this is what the operator intended. As another example ofsuch a feature, when the hitch is above the PTO OFF set point, operatorstation-mounted PTO switch 1 is in the ON position, and auto PTO modeswitch 5 is moved from its AUTO PTO ON position to its AUTO PTO OFFposition, PTO indicia 40 will flash and the PTO shaft will be disableduntil operator station-mounted PTO switch 1 is cycled from its ON to itsOFF position and back to its ON position.

The AUTO PTO mode described herein is a feature that adds significantfunctionality to the PTO control system of FIG. 2. However, the AUTO PTOfunction is only needed when the work vehicle is traveling (e.g., theapplication shown in FIG. 1A), not when the work vehicle is stationary(e.g., the application shown in FIG. 1B). Thus, according to anotherfeature of the PTO control system, control circuit 64 receives a vehiclespeed signal from vehicle speed sensor 25 and, when the speed is below apredetermined vehicle speed (e.g., one mile per hour or less), controlcircuit 64 disables the AUTO PTO function. This feature preventsinadvertent engaging and disengaging of the PTO based on the hitchposition when vehicle 10 is stationary. While this feature hasparticular applicability when automatic engagement and disengagement ofthe PTO is based on hitch position, it may also find applicability whensaid automatic engagement and disengagement of the PTO is based on otherinputs, such as, an “end of row” command received from anoperator-adjustable switch or from control circuit 64 in which aplurality of end-of-row functions (e.g., control of mechanicalfront-wheel drive, differential lock, etc.) occurs in response to asingle command.

According to one embodiment of this feature, if the operator actuatesauto PTO mode switch 5 to the AUTO PTO ON position when the speed isbelow the predetermined vehicle speed, the AUTO PTO function will not beenabled and auto PTO indicia 42 will flash to indicate to the operatorthat the AUTO PTO function cannot be enabled. According to anotherembodiment of this feature, when in AUTO PTO mode, if the hitch is abovethe AUTO PTO OFF set point and the work vehicle 10 does not move for apredetermined period of time (e.g., 10 seconds), the AUTO PTO mode isautomatically disabled and auto PTO indicia 42 flashes. Otherembodiments of disabling AUTO PTO based on a vehicle speed signal arecontemplated. The value of the predetermined vehicle speed may beadjustable by a service technician or programmed during manufacturing.The value is preferably sufficiently low to indicate the absence ofvehicle motion in spite of the standard tolerances of vehicle speedsensor 25.

Several other features of the present control system also relate todisabling the AUTO PTO mode. According to one feature, when either ofthe remote PTO switches 22, 24 is actuated, AUTO PTO is disabled.According to another feature, if the hitch is above the AUTO PTO OFF setpoint and remote hitch control switch 23 is actuated, AUTO PTO isdisabled. According to a further feature, if the hitch is above the AUTOPTO OFF set point and there is no hitch movement for a predeterminedtime (e.g., one minute), AUTO PTO is disabled. According to yet anotherfeature, an operator station seat position sensor is provided toindicate whether the operator is in the seat of the operator station.The operator station seat position sensor provides a seat positionsignal to control circuit 64. If the operator station seat positionsignal indicates the operator is off the seat for more than apredetermined time (e.g., five seconds), AUTO PTO is disabled.

While the embodiments illustrated in the FIGURES and described above arepresently preferred, it should be understood that these embodiments areoffered by way of example only. For example, the principles of thepresent invention may find applications in construction machinery aswell as agricultural machinery. In another alternative embodiment, anadditional remote throttle switch may be provided to allow the operatorto adjust the PTO speed by, for example, remotely adjusting the enginespeed or remotely adjusting a gear coupled to the PTO shaft. Theinvention is not limited to a particular embodiment, but extends tovarious modifications that nevertheless fall within the scope of theappended claims.

What is claimed is:
 1. A control system for controlling a power takeoffshaft of a work vehicle, the work vehicle configured for travel across awork surface and having an operator station, the control systemcomprising: a remote switch located remotely from the operator stationto generate at least one remote switch signal; a vehicle speed sensor toprovide a vehicle speed signal representative of a speed of the workvehicle relative to the work surface; and a control circuit coupled tothe remote switch and the vehicle speed sensor, the control circuitcontrolling the operation of the power takeoff shaft dependent upon theremote switch signal when the vehicle speed is below a predeterminedvehicle speed and controlling the operation of the power takeoff shaftindependent of the remote switch signal when the vehicle speed is abovethe predetermined vehicle speed.
 2. The control system of claim 1, theremote switch to provide a remote switch signal representative of arequest to engage or disengage the power takeoff shaft, and when thevehicle speed signal exceeds the predetermined vehicle speed, thecontrol circuit to prevent engagement and disengagement of the powertakeoff shaft based on the remote switch signal.
 3. The control systemof claim 1, the control system further comprising an operatorstation-mounted switch to provide a local switch signal to control thepower takeoff shaft, the control circuit coupled to the operatorstation-mounted switch to selectively control the power takeoff shaftbased on the local switch signal.
 4. The control system of claim 1,wherein the remote switch includes a pair of momentary pushbuttons, thefirst momentary pushbutton to provide an ON remote switch signal and thesecond momentary pushbutton to provide an OFF remote switch signal. 5.The control system of claim 1, wherein the remote switch includes afirst remote switch coupled to the work vehicle at a first location anda second remote switch coupled to the work vehicle at a second location,the first and second locations being on opposite sides of the powertakeoff shaft.
 6. The control system of claim 1, wherein the vehiclespeed sensor includes a ground speed radar.
 7. The control system ofclaim 1, wherein the predetermined vehicle speed is approximately onemile per hour.
 8. The control system of claim 1, wherein the vehiclespeed sensor includes a transmission output speed sensor.
 9. A controlsystem for controlling a power takeoff shaft of a work vehicle,comprising: remote switch means for providing at least one remote switchsignal; sensor means for providing a vehicle speed signal representativeof a speed of the work vehicle; and control means coupled to the remoteswitch means and the vehicle speed sensor means for controlling theoperation of the power takeoff shaft dependent upon the remote switchsignal when the vehicle speed is below a predetermined vehicle speed andfor controlling the operation of the power takeoff shaft independent ofthe remote switch signal when the vehicle speed is above thepredetermined vehicle speed.
 10. The control system of claim 9, thecontrol system further comprising operator station-mounted switch meansfor providing a local switch signal to control the power takeoff shaft,the control means coupled to the operator station-mounted switch meansto selectively control the power takeoff shaft based on the local switchsignal.
 11. The control system of claim 10, further comprising means forselecting one of the local switch signal and the remote switch signal tocontrol the power takeoff shaft.
 12. The control system of claim 9, theremote switch means including a pair of momentary pushbuttons, the firstmomentary pushbutton to provide an ON remote switch signal and thesecond momentary pushbutton to provide an OFF remote switch signal. 13.The control system of claim 9, wherein the predetermined vehicle speedis one mile per hour.
 14. The control system of claim 9, wherein themeans for sensing comprises a transmission output speed sensor.
 15. Amethod for controlling a power takeoff shaft of a work vehicle, the workvehicle configured for travel across a work surface, the methodcomprising: providing at least one remote switch signal; providing avehicle speed signal representative of a speed of the work vehiclerelative to the work surface; and controlling the operation of the powertakeoff shaft dependent upon the remote switch signal when the vehiclespeed is below a predetermined vehicle speed and controlling theoperation of the power takeoff shaft independent of the remote switchsignal when the vehicle speed is above the predetermined vehicle speed.16. The method of claim 15, wherein the predetermined vehicle speed isapproximately one mile per hour.
 17. The method of claim 15, wherein thestep of providing a vehicle speed signal comprises providing a signalrepresentative of transmission output speed.
 18. The method of claim 15,further comprising providing a local switch signal to selectivelycontrol the power takeoff shaft.
 19. The method of clam 15, furthercomprising selecting one of the local switch signal and the remoteswitch signal to control the power takeoff shaft.